I saw this setup in an RV magazine while in the dr. waiting room. Since it's attached directly to the RV or 5th wheel, you probably don't need a tag on it. I figured if it can carry a GoldWing, it can carry a Valkyrie. Look around on the website, I think they have one that's tandem...for a bike and car to be towed.
http://www.cruiserlift.com/swivelwheel58.html